Human MP52 was first isolated for its CDNA as an osteogenetic factor belonging to TGF-.beta. gene superfamily in 1994 (Biochem. Biophy. Res. Comm., Vol. 204, No. 2, 1994). Human MP52 is considered as a protein having 120 amino acid residues with alanine at the N-terminus, and its amino acid sequence is reported in WO93/16099 and WO95/04819. It is evident from various animal tests that MP52 is involved in osteogenesis similar to other osteogenetic factors. However, there have been left many unknown points in reference to by what MP52 is directly induced in osteogenesis and by what mechanism osteogenesis is performed, and there have been issued only a few reports thereon.
In addition, mouse MP52 is different from human MP52 in only one of the amino acid sequence at the N-terminal site, and thus MP52 is derived from a gene firmly preserved over species so that it is not that easy to obtain an antibody to human MP52 from a mouse, although it was reported in WO93/16099 that a mouse monoclonal antibody became available.